Ishaan is 4 times as old as Christopher and is also 24 years older than Christopher. How old is Christopher?
Solution: We can use the given information to write down two equations that describe the ages of Ishaan and Christopher. Let Ishaan's current age be $i$ and Christopher's current age be $c$ $i = 4c$ $i = c + 24$ Now we have two independent equations, and we can solve for our two unknowns. Since we are looking for $c$ , and both of our equations have $i$ alone on one side, this is a convenient time to use elimination. Subtracting the second equation from the first equation, we get: $0 =$ $4c$ $-$ $ (c + 24)$ which combines the information about $c$ from both of our original equations. Solving for $c$ , we get: $3 c = 24$ $c = 8$.